Formaldehyde as an assistant in the dyeing of polyester fibers and blends thereof athigh temperatures



FORMALDEHYDE AS AN ASSISTANT IN THE DYEING F POLYESTER FIBERS AND BLENDS THEREDF- AT HIGH TEMPERATURES Ferdinand Schulze, Wilmington, Del., assignor to E. I. A

du Pont de-Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Application August 22, 1955 Serial No. 529,893

6 Claims. (Cl. 8-55) This invention relates to pressure dyeing of synthetic fibers, more particularly to dyeing fibers from synthetic linear polyesters of U. S. 2,465,319 and wool blends thereof.

The full commercial potential of these fibers is still unrealized, mainly because of their resistance todyeing. Particularly the dyeing of blends of polyester fibers with wool and otherprotein fiberspresent different problems one of them being the off-tone staining of dyes on wool. Furthermore, the full strength of dyes on polyester fabrics cannot be reached in conventional dyeing equipment and wool; blends of polyester fabrics cannot be dyed. stainless in a one-stepprocess. 7

The principal object of the present invention is, therefore, an improvement inthe dyeing of linear polyester fibers and their blends with protein fibers. Other objects will become apparent from the description which follows.

These objects are accomplished by addition of formal dehyde in any form such as formalin or para-formaldehyde to the dye bath and the dyeing. in high-temperature dyeing equipment at 225250 F. It has been found that formaldehyde yields greater color value and brightness of shade on polyester fibers with less staining: on the protein fiber component of. blends therewith. No deleteriousaction of formaldehyde on dispersed dyes has been observed, andanystaining on protein fibers by the dispersed dyes is on-tone. Wool pretreatments with formalin, known from the literature, have been concerned principally with decreasing its alkali solubility. Further, it was found that to obtain a. shade equivalent to the one produced at 212 F. only about 75% of the wool color was required at 250 F. The use of formalin at 250 F. also yielded an increase of about 10%. shade. depth on polyester fibers in the blend.

According to the present invention, the fabricsare dyed in one bath in the presence of 1-10 g./l. formalin in a pH range of 4.0-5.5, and at 250 F. Suitable dyeings have been made on polyester-wool blends with a combination of dispersed dyes with neutral dyeing, milling, acid types,-premetallized neutral dyeing, and premetallized strong acid dyeing colors. Neutral dyeing or strong acid dyeing wall dyes can also be applied by two-step, onebath, union-dyeing processes, wherein the wool is protected with formaldehyde during the 250 F. polyester fiber dyeing cycle and the bath is then respectively neutralized or acidified strongly for the wooldyeing cycle,

which may be at lower temperature. The two-step dyeing process may be reversed; either the protein or the polyester fibers may be dyed first. Material and time savings make the 250 F. dyeing process very attractive economically compared to conventional dyeing processes. High temperature dyeing of wool or other protein fibers becomes feasible by use of formaldehyde. Short dyeing cycles for wool in the apparatus disclosed in Cole S. N. 347,263, filed April 7, 1953, known as a Barotor or in other high temperature dyeing equipment, thus becomes more practical. A

' I A scoured, blended fabric of 45% wool and 55% poly- ICC . 2' The following examples illustrate the present invention without limiting. it:

Example I V Samples of 100% polyester fabric and samples of 100% wool fabrics were dyed together in pressure tubes at 250 F. The aqueous dye baths made up to a ratio of 40:1 contained 6% acetic acid, 1% of a non-ionic surfactant withgooddetergent. and dispersing properties, and the dye in a concentration of 0'.5-2% by weight of fabric. Two series of dyeings, without and with 5 g./l. of 37% formaldehyde, gave the following comparison:

Dye Polyester Fiber Wool Stein 7 Dyeing 1% 4-anilino-3-n1troben- Much brighter than Lighter than conzenesullanilida. v control. trol. 1% Oelanthrene Yellow Brighter than controL- D0.

GL Prototype No. 534

from the .AATCO yearbook. 0.5% The dye obtained by do Light tan yellow;

- coupling aminoazobencontrol gray yelzene with henollow.

Formaldehyde produced no detectable differencesin light fastness in the Dacron dyeings. The results in this table illustratef clearly the improved brightness on polyester fibers and decreased stain on wool with the use of formaldehyde in the dye bath.

' Example I I ester fiber was loaded on the rotor of a Barotor? (Cole S. N. 347,263) andrescoured ma 1% ammonia solution for 15 minutes at 160 F. This aqueuos solution was replaced by enough water to give the dye bath a ratio of 2011-30zl. The water was heated to 160 F. and the pasted combination of 1.25% l-hydroxy-4- toluino-anthraquinone, 0.5 methoxypropylimide of 1,4- diaminoanthraquinone-Z,3-dicarboxylic acid, 0.5% of'the dye obtained by coupling aminoazobe'nzene with phenol, 0.5% of the chromed dye of Example I in U. S. 2,508,404, 0.36% of the dye of prototype No. 144 from AATCC yearbook, 1% Sandopan TFL (a sulfonated fatty amide, marketed by Sandoz), 1% Emulphor ON (a water-soluble polyethylene ether of a fatty alcohol), and 3% of 70% glycolic acid was added at this temperature. The bath was then heated to 212 F. with the top vent open; the vent was closed and 3 g./l. of 37% formaldehyde was added. The bath was heated to 250 F. and the dyeing continued for 1.5 hours. Adjustments toshade were made during this period. The bath temperature was then dropped and the fabric rinsed for a few minutes with cold water. This navy dyeing, was scoured to minimize solvent bleeding. Water was added to the Barotor to usual bath ratio and 1%, based on bath volume, of the following self-emulsifying mixture was added: parts Varsol (a refined aliphatic hydrocarbon solvent, marketed by Esso Standard Oil), 5 parts Emulphor ON, and 5 parts Duponol RA (fortified ether-alcohol sulfate, marketed by du Pont). The scour was run 15 minutes at 180 F, the-bath temperature was dropped, and'afinal scour was given with 0.5 (by weight of fabric) Emulphor ON at F. for 15 minutes, after which the fabric was rinsed and dried. Shade and fastness were equivalent to an atmospheric pressure dyeing dyed in a bath of higher dye concentration using dye carriers such as ophenylphenol. Another feature is the shorter dyeing cycle in this single-bath, one-step process.

Example III In a small Barotor samples of polyester fabrics and wool blends therewith were dyed at 250 F. i n baths containing the dye formulation of Example II for a navy Example IV A one-bath, two-step modification of the previous process is illustrated for producing a brown shade, using metallized dyes for the wool. At 160 F., a paste of 0.65% of the dye obtained by coupling aminoazobenzene with phenol, 0.15% 1-hydroXy-4-toluino-anthraquinone, 1.2% methoxypropylimide of 1,4-diaminoanthraquinone- 2,3-dicarboxylic acid, 0.9% of the chromed dye of EX- ample I in U. S. 2,499,133, 0.15% of the cobalted dye obtained by coupling 2-aminophenol-4-sulfonamide with 2-naphthol, 0.5% of the dye of prototype number 146 in the AATCC, 1.4% 1-amino-2-methoxy-4-hydroxy-anthraquinone, 1% Emulphor ON, and ammonium acetate was added, the temperature raised to 212 F. and the wool dyeing continued for 1 hour. To dye the polyester in the fabric, and to protect the wool portion in it, 5 g./l. of 37% formaldehyde and 6% acetic acid by weight of fabric were added and the bath kept at 250 F. for 1.5 hours with closed top vent. The bath temperature was dropped, the fabric rinsed, and scoured with 0.5% Emulphor ON at 160 F. for 15 minutes.

Example V A strongly acid dyeing was made with the following dye paste, added to the *Barotor at 160 F.: 1% 4-anilino-3-nitrobenzene sulfanilide, 2% methxypropylimide of 1,4-diaminoanthraquinone-2,3-dicarboxylic acid, 0.5 Pontacyl Green NV (Color Index No. 735), 6% acetic acid, 1% Emulphor ON, 1% Duponol RA, and 5 g./l. formaldehyde 37%. The polyester fiber was dyed first at 250 F. for 1.5 hours, the bathtemperature was dropped to 212 F., 6% sulfuric acid was added, and the wool was dyed at this temperature for 1.5 hours. The fabric was rinsed and scoured with 0.5 Emulphor ON at 160 F. for 15 minutes.

Modifications of the above dyeing cycles are also possible, e. g., dyeing the wool at 225 F. In the presence of sulfuric acid, formaldehyde provides only partial protection to wool at 250 F., but satisfactory results may be obtained inthis bath at 225 F.

While the invention has been illustrated using certain dyes, it is to be understood that the invention is not limited to those disclosed, but any dye or combination of dyes which are used commercially on polyester fibers or fabrics may be used according to the present invention with the formaldehyde and high temperature procedure.

The present invention is applicable to 100% polyester fiber fabrics, i. e., the fibers of U. S. 2,465,319, alone or in combination with wool or other protein fibers. The invention is primarily concerned with the dyeing of polyester fibers to produce more intense shades without increasing the amount of dye used, or to obtain the same shade with less dye. In addition the formaldehyde serves the additional purpose of protecting wool when present against degradation. In the claims the term polyester is intended to have the same significance as in the patent. The benefits realized on fabrics are generally obtained when applied to stock, top, and yarn dyeing at high temperatures. The addition of formalin gives the wool in the blend a protection again degradation. The highest degree of protection is realized at a pH of 4.0-5.5, although appreciable protection is obtained at higher or lower pH. The addition of l10 g./l. of formaldehyde will protect wool from tendering in aqueous baths at elevated temperatures from 225250 F. Below 1 g./l. of formaldehyde, the protection is not snfiicient. On the other hand, no economical advantage is usually achieved by addition of more than 5 g./l. Very good results are obtained with 3 g./l. of formalin. Other ingredients have also been used in the place of formaldehyde, but none of them gave the multiple effect of protecting protein fibers in a high temperature union dyeing, decreasing their off-shade staining, and increased dye absorption of the polyester portion.

The new method relates to dye baths containing dispersed dyes for polyester fibers and, in the case of protein fiber blends therewith, wool dyes for the protein 3 fibers. As an illustration, the following applicable dye classes are listed; for the polyester fiber: acetate dyes, such as the Celanthrene and Acetamine dyes, and for the protein fiber portion in blends: chrome dyes, acid dyes, anthraquinone acid dyes, milling dyes, and premetalliz ed acid dyes.

The advantages of the present invention are the improved brightness of dyeings on the polyester fibers,- the on-tone staining on wool in blends therewith, and the L reduced degradation of wool in union dyeings.

Itwill be apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, and therefore it is not intended to be limited except as indicated in the appended claims.

I claim:

1. The process of dyeing linear glycol-dibasic acid polyester fibers and fabrics made therefrom which comprises subjecting the same in a dyeing bath having a pH between about 4.0 and 5.5 to a temperature of 225 F. to 250 F. in the presence of formaldehyde, said dye bath containing a dispersed dye for the said polyester fibers.

2. The process of claim 1 in which formaldehyde is present in amount equivalent to that obtained by the addition of 1 to 10 grams per liter of 37% formalin to the said bath.

3. The process of claim 2 in which the formaldehyde present is equal to a concentration of 3 grams of 37% formalin per liter of bath.

4. The process of claim 1 in which a fabric consisting of glycol-dibasic acid polyester fibers is dyed with a dispersed acetate dye.

5. The process of claim 1 in which a fabric containing wool is dyed.

6. The process of claim 4 in which the fabric contains approximately 45% wool and 55% polyester fiber and the dye bath contains a dispersed acetate dye for the polyester and an acid dye for the wool.

, References Cited in the file of this patent Modern Textiles for January 1955, pages 43 and 88. 

1. THE PROCESS OF DYEING LINEAR GLYCOL-DIBASIC ACID POLYESTER FIBERS AND FABRICS MADE THEREFROM WHICH COMPRISES SUBJECTING THE SAME IN A DYEING BATH HAVING A PH BETWEEN ABOUT 4.0 AND 5.5 TO A TEMPERATURE OF 225*F. TO 250*F. IN THE PRESENCE OF FORMALDEHYDE, SAID DYE BATH CONTAINING A DISPERSED DYE FOR THE SAID POLYESTER FIBERS. 